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40

Moulders' Tools.

I:!

same time rapping the pattern carefully to prevent the sand adher-
ing, and a few points should here be noticed as regards the finish-
ing of the mould. The moulder uses trowels, and c sleeker*,'
(which last are only trowels of special shapes) to smooth away any
broken portion, but, if the mould is made too smooth, there Is
great danger of blistering or scabbing, from the fact that the
mould, having lost to some extent its porosity, refuses to allow the
escape of gas, and it is generally understood by moulders that
the hand makes the best trowel, though certainly it is always
better to let a mould remain, if possible, just as the pattern left it.
In Fig. 52, a few moulders' tools are sketched.

The upper box is usually
termed the 'cope? which also
applies to the outer mould, and
the lower box is .sometimes
called the 'drag* The rope
should be well weighted to
ensure sound castings. \Vhen
two boxes are used, they fit to-
gether as shewn in Fig. 2, and
can be easily replaced, but
if the floor serves as bottom
box, exact correspon- Vr>i*r
dence is obtained by
driving stakes into the
ground through the
lugs of the top box.
-^                    Cbaplets have been

TfaolS.         mentioned, and are

to stay cores that cannot be

otherwise   supported;  their use,  however, is not advisable,  for
they tend  to produce weakness in the casting in  which
remain.    They should be tinned, or at least freed from rust, to
ensure uniting with the casting.

We have already described the charging of the cupola;  it
remains for us to explain the method of tapping it    The
at the cupola is provided with two iron rods; one he         to
a hole-in the clay stopping, which he does as soon as the